L12 : Electric Bell - Electric Current & Circuits, Science, Class 7 Video Lecture

hello friends this video on electric
current and its effects fat12 is brought
to you by exam four calm no more fear
from exam so let us first look at the
construction of electric pen normally
you would have seen this type of bell
especially present in offices so when
you just press it and you get a sound
right so what is it made of all so once
we know the construction only then we
will be able to understand it's working
so it basically consists of a wild so
here you have the wire which is turned
around the iron piece which forms the
coal so the wild and the iron piece this
iron piece forms the core of the
electromagnet and the wildest turn
around
overhead and these two together form the
electro magnet so you have this entire
setup of electro magnet here then you
have a hammer which you can see here you
have this hammer now whenever the hammer
will strike the gong a sound will be
produced so that is where the sound gets
produced when we press the electric pen
you have an iron strip so this iron
spread gets attached to the
electromagnet so if you see here you
have an iron strip here which is kind of
attached to the electromagnet when
current flows through it so we will see
how does that happen
you also have a contact screw so this is
the contact screen here so sometimes
when current flows through it it will
come and then sometimes it will come in
contact sometimes it will leave the
contact so we will see how the contact
forms and breaks so we will see that
when we talk about the working so these
are the basic important parts of the
electric band so you have the
electromagnet here you have the iron
strip here you have the contracts
contact stream here the hammer and the
gong so let us now look at the working
of an electric pen now what happens is
when we switch it on so initially this
is the initial condition
and this is the final condition when
current flows through the circuit so in
the initial condition the switch is off
so there is no current which is flowing
through the circuit through the wires so
therefore it is this is how the setup is
now when we switch it on then what
happens current flows through this
electromagnet through these wires now as
current flows through this wire the
magnetic effect is produced that is a
magnetic field is reduced surrounding
this area now this magnetic field is
experienced by this soft iron strip so
when current flows through the wire this
soft iron strip gets attracted so as you
can see here here it was in this
position now it gives attracted so it's
like he moves towards the electromagnet
now as it gets attracted it moves this
side so what happens this part tack
which was initially existed now the
contact breaks so you see the contact
breaks there is no more contact while it
moved this way because this also moved
in this way now as this moves this side
what happens this hammer also moves in
this direction and the hammer strikes
the gong and when the hammer strikes the
gong
a sound is produced and now you see what
happened now as since the contact broke
what happened now the circuit is no more
complete because there is a break in the
circuit now when the circuit is no more
complete what will happen now the
electric current will stop flowing
now when the electric current stops
flowing then what then again it goes
back to condition 1 then no current is
flowing correct again when current
starts flowing it comes back to its
coming stage - and that's how this
entire process repeats and as a result
every time the hammer strikes the form
we hear a sound and that is how electric
then produces sound so you see here the
main role is being performed by the
electromagnet because it is due to the
electromagnet that this contact forms
and breaks forms and breaks so that
happens because the electron
now since an electromagnet it becomes
very easy to produce the magnetic field
and to remove the magnetic it just by
controlling the current so there that is
the most important advantage of
electromagnet over permanent magnets so
in this scenario we cannot think of
using a permanent magnet in it and other
than in instead of the electromagnet
because had it been a permanent magnet
we cannot switch on and off the magnetic
effect of that magnet right so that's
the main advantage of electromagnet and
this is how electric bail works so let
us have a quick recap as we saw that
current flows through the closed circuit
so when it is connected to the battery
and everything so current flows through
the circuit as a result coil wound
around iron core acts as electromagnet
so the iDEN strip gets attracted so this
island strip will get attracted towards
the electromagnet as a result the
contact with the screw when they broken
and as a result of this the hammer would
strike the bond as soon as the hammer
strikes the bomb this since it has
broken so the circuit is now open
circuit therefore no current will flow
through the circuit now when no current
flows this doesn't behave like an
electromagnet anymore that means it
doesn't produce any magnetic field and
the islands trip goes back to the
original position so basically the
reverse thing is happening now contact
with the screw develops again and again
the closed circuit now so has the
contact develops it is a closed circuit
again current flows through the circuit
and this process keeps repeating so
every time the circuit is closed
the hammer would strike the gong and the
sound will be produced thank you please
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